The invention relates to a camshaft adjusting system according to the preamble of the independent claim.
Camshaft adjusting systems consist of a number of different components. The number of the components may vary, although a common feature of many camshaft adjusting systems lies in the presence of a camshaft adjusting device and a control valve or a control valve group. There are different types of camshaft adjusting devices, all of which can rotate the relative position of a camshaft with respect to a further shaft, such as the crankshaft, of an internal combustion engine. One type of camshaft adjusting device which is frequently used is the oscillating motor camshaft adjusting device. An oscillating motor camshaft adjusting device is a rotatory vane-type motor which converts the hydraulic pressurization of one chamber with respect to another chamber into rotatory movement. The two chambers, which act in opposition, are separated by a mobile vane which changes the position according to pressure ratios. The camshaft, which is connected to the camshaft adjusting device, is in turn entrained and rotated in its position as a result of the change in position. The number of chambers of one direction of action, the number of vanes and the number of chambers of the opposite direction of action frequently correspond. Chambers of the same type are hydraulically interconnected. The chambers lead to a control valve group or a control valve. The functionality of a large-scale integrated control valve can be imitated through a skillful connection of a plurality of control valves. Considered in hydraulic terms, control valve groups consisting of a plurality of valves are consequently similar to control valves which consist of a single control valve provided with a plurality of connections. It is therefore to be assumed that the chambers of the first direction of action are all directly or indirectly interconnected and the chambers of the second direction of action lead to a further connection of the control valve group. The connections A and B are referred to in simplified terms.
It is desirable to know the relative position of the camshaft with respect to its reference shaft, in particular in the case of extraordinary operating states of the internal combustion engine. The patent literature discloses numerous proposals in which a defined position can be deduced by using special locking mechanisms. An example can be found in the German patent application DE 102004012460 A (HYDRAULIK-RING GMBH). - - - ., in which locking positions can be selected and planned through a skillful combination of a camshaft adjusting device with a spring.
Other areas of hydraulic motor vehicle technology disclose particular valves which, through their configuration, produce delays of a switching response in selected operating states.
DE 19816069 A (HYDRAULIK-RING GMBH). - - - . describes a valve which can preferably be used for automated manually shifted transmissions. A piston, which can be pressurized on both sides and which separates two pressure spaces from one another, is controlled via a valve with a safety function. In the zero switched position, the safety position, the three-way proportional valve does not have to close the coupling suddenly in the case of a disturbance.
Other valves which can be used with camshaft adjusting devices can be found in CN 2592932 Y (ZHONG WEISHING).Dec. 5, 2002. and in EP 1316733 A (SIMEONI S.R.L.).Sep. 23, 2002.
The inventors of the present invention were searching for a possibility, as simple and reliable as possible, of producing a defined state in a camshaft adjusting system. For this purpose they considered both changing the camshaft adjusting device in terms of components and taking action in the camshaft adjusting system at other locations, such as at the control, for example.
DE 10344816 A (AISIN SEIKI). - - - . presents a 7/6-way valve which, when the internal combustion engine is switched off, this being called the engine stop signal in the publication, moves a camshaft adjusting system into a particular state by supplying a sufficient quantity of electricity from an ECU in order to initiate a fluid drain function through setting a first regulating mechanism, the response of a blocking mechanism and setting a second regulating mechanism. Not only is it undesirable to integrate 7/6-way valves of a long construction into a cylinder head, but the camshaft adjusting system also requires turn-off run-down times instead of using the start delays for timing adjustment processes. Furthermore, a distinction is made in the method disclosed here between many different states when switching off in the camshaft adjusting system and when draining oil. The approach which is disclosed here appears to lie in constructing a highly complicated system having disadvantages due to its components.